Predicting Adhesive Bond Performance Based on Initial Dielectric Properties

Abstract

In recent years, there has been a widespread growth in the application of composite materials particularly in the Aerospace and Automotive sectors. This is because composite structures are generally comparatively light in weight and provide corrosion and wear resistance as compared to metals or ceramics. Due to the strict fail-safe philosophy of the aerospace industry, the certification approach for current practice in joining composite materials is to thicken the joining areas and to use numerous fasteners which in turn increases the weight and stress concentrations in the structure. The use of adhesive bonding can improve the stress distribution between the composite materials / dissimilar materials and can contribute to a lighter structure. However, there much investigation is yet to be done in this discipline to predict the bond strength and performance using non-destructive evaluation methods. This paper will focus on an approach to study the mechanical as well as the dielectric properties of an adhesive bond. The dielectric testing is done by using Broadband Dielectric Spectroscopy (BbDS), wherein the dielectric characteristics of the material are analyzed in a wide frequency spectrum. The data obtained by this technique are used to demonstrate the charge transport, the combined dipolar fluctuation, and the effects of polarization occurring between the boundaries of materials. The continuous modifications of the dielectric spectra are due to the changes in the electrical and structural interactions between the particles, shapes, and orientations of the constituent phases of the morphological structure of the material system. Information about the morphologies, impurities/contamination or interaction of the dissimilar surfaces of the pristine bond can be obtained from the initial BbDS properties. The dielectric properties for adhesively bonded composites with different surface adhesion properties have shown promising evidence of predicting the final mechanical performance of the bonded material system. The success and limitations of this approach will be discussed, and needs for continued investigation identified

Symmetrical “Sandwich” Polybutadiene Film with High-Frequency Low Dielectric Constants, Ultralow Dielectric Loss, and High Adhesive Strength

“…To assure high-speed signal transmission and low signal transmission loss, the dependence of the dielectric properties on the frequency is plotted in Figure S3 and Figure . The polarization response of the polymer material to the electric field frequency shown in Figure d indicated dielectric properties and their regions of interfacial and space charge, orientation, atomic (ion), and electronic polarization . For the nonpolar cross-linked polybutadiene adhesive system, the polarization strength of vinyl with isolated π electron played an important role at the high-frequency electric field.…”

Multistructural Network Design Enables Polybenzoxazine to Achieve Low-Loss-Grade Super-High-Frequency Dielectric Properties and High Glass Transition Temperatures

“…As shown in Figure S27 and Table , the dielectric constant values display dependence on the measurement frequencies. Generally, there are four polarization types (i.e., interfacial and space charge, orientation, and atomic (ion) and electronic polarization) . The polarization mechanisms have their corresponding effective frequency ranges.…”

“…Advanced super-high-frequency communications can satisfy the future demand for faster internet connections and increased device access. However, mutual interference easily occurs during super-high-frequency transmission, leading to a resistance–capacitance time delay, an increase in crosstalk, and more energy consumption. , As shown in eq , the signal transmission speed ( V ) is inversely proportional to the square root of dielectric constant ( k ) value of the polymeric materials: , where c is light speed. Furthermore, the signal propagation loss rate ( L ) is proportional to the frequency ( F ), dielectric loss (tan δ, f ), and square root of k (eq ): , where the prefactor K is a constant.…”

State Variable Methods of Assessment, Prognosis, and Control of Composite and Bonded Structures

“…One of the most remarkable capabilities of the dielectric material state determination method is to detect and predict the strength of bonded materials, especially the strength of bonded heterogeneous materials. Banerjee, et al have pioneered this method development, and much current research is underway in our group [10]. This topic deserves much more space that we have in this discussion, but an example of the capabilities will be provided.…”

“…Changes in the normalized average Dielectric Relaxation Strength (DRS) of bonded composite joints as a function of the surface treatment of the adherents[10].…”